I changed the oil in the 16 hp engine today. The manual calls for 10 - 30. I had a a brain snap and grabbed a bottle of 10 - 40 Castrol conventional. Poured it in when I'm cleaning up I look at the label and realize it was wrong. Does it matter? Will it be hard starting in the cold temperatures? I'm inclined to drain it and put that oil in my car and put in the right grade. Am I being annal retentive?